diff --git a/nixos/doc/manual/release-notes/rl-2009.xml b/nixos/doc/manual/release-notes/rl-2009.xml
index 9bbbecc0569..31cabce1d53 100644
--- a/nixos/doc/manual/release-notes/rl-2009.xml
+++ b/nixos/doc/manual/release-notes/rl-2009.xml
@@ -110,6 +110,15 @@ systemd.services.mysql.serviceConfig.ReadWritePaths = [ "/var/data" ];
 </programlisting>
     </para>
    </listitem>
+   <listitem>
+    <para>
+      Two new option <link linkend="opt-documentation.man.generateCaches">documentation.man.generateCaches</link>
+      has been added to automatically generate the <literal>man-db</literal> caches, which are needed by utilities
+      like <command>whatis</command> and <command>apropos</command>. The caches are generated during the build of
+      the NixOS configuration: since this can be expensive when a large number of packages are installed, the
+      feature is disabled by default.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>